This description relates to fuel cells.
In a polymer electrolyte fuel cell (PEFC), an electrically non-conducting, proton permeable polymer electrolyte membrane (PEM) separates the anode and cathode of the fuel cell. On the anode side of the fuel cell, fuel is oxidized to produce protons and electrons when the fuel is hydrogen. If the fuel is a hydrocarbon derivative or a functionalized hydrocarbon such as methanol or ethanol, for example, the fuel is oxidized to form protons, electrons, and carbon dioxide. The protons are driven through the PEM to the cathode. On the cathode side of the fuel cell, protons passing through the PEM are combined with oxygen atoms and electrons to form water.
If unreacted fuel reaches the cathode side of the fuel cell, the efficiency of the fuel cell decreases because unreacted fuel does not contribute to the power output of the cell. Furthermore, the fuel can be oxidized at the cathode and may also flood the cathode-side catalyst. Unreacted fuel may reach the cathode by diffusing through the PEM, which usually referred to as crossover. Unreacted fuel may also reach the cathode by leaking around the membrane electrode assembly (MEA), which includes the PEM, an electrocatalyst, and a diffusion layer.
The MEA may be sealed to the fuel cell housing using a gasket to prevent fuel leakage around the MEA. The gasket, however, must be able to withstand the severe electrochemical environment at the anode and cathode and maintain a seal throughout the life of the fuel cell. Silicone is commonly used as a gasket material because of its low cost and ease of fabrication. Silicone, however, degrades under fuel cell operating conditions. PTFE is also commonly used as a gasket material but is expensive relative to the silicones and rubbers typically used in sealing applications. While PTFE can Initially be compressed to form a seal, it tends to relax over time such that leaks form around the seal. Therefore, there remains a need for gaskets that can maintain a seal for the MEA over the life of a fuel cell.